1. Field of the Invention
This invention relates to an optical apparatus having diopter correcting means, and particularly to an optical apparatus having diopter correcting means suitable, for example, for a camera, binoculars or the like which is adapted to detect whether an observer wears spectacles or contact lenses and to automatically appropriately set the diopter of an optical system into which the observer looks.
2. Related Background Art
Generally, the correction of the diopter of an optical apparatus such as the finder of a camera or binoculars has been accomplished by manually moving a portion of an eyepiece optical system to adjust it to a position one can readily see.
Also, Japanese Laid-Open Patent Application No. 63-206731 proposes a finder apparatus adapted to detect a value related to the refractive power of the eye of an observer looking into a finder by an eye refractometer, and to effect the correction of the diopter of a finder optical system in conformity therewith.
On the other hand, as an apparatus having a similar optical construction, a camera having a visual axis detecting unit is proposed in Japanese Laid-Open Patent Application No. 4-138431 and Japanese Laid-Open Patent Application No. 4-138432.
These publications propose a camera having a visual axis detecting unit adapted to detect by a spectacle detecting portion provided in a portion of the camera whether a photographer is using spectacles, and to adjust the construction of light receiving means on the basis of a signal from the spectacle detecting portion.
In the above-described apparatus wherein diopter correction is manually effected, each time a state in which observation is done (hereinafter simply referred to as the observation state), such as whether the observer is observing while wearing spectacles or contact lenses or observing by the naked eye, changes, it is necessary to manually readjust the diopter, and this has led to the problem that operation is cumbersome.
Also, the finder apparatus of the aforementioned Japanese Laid-Open Patent Application No. 63-206731 is effective when highly accurate diopter correction is effected to many and unspecified observers, but it is too large-scale in apparatus construction as an apparatus for use by ordinary substantially limited observers. Particularly it has been difficult to apply it to an apparatus to the portability of which importance is attached.
Generally, to an observer who usually wears spectacles, there has been the problem that when conditions such as temperature and humidity are bad or suddenly change, the spectacles sometimes become clouded and any other apparatus than an apparatus which enables observation to be readily made in other observation state (for example, a state in which the observer has taken off the spectacles) is difficult to use.